As semiconductor devices are developed with high integration, the size of patterns required for a semiconductor device is getting smaller. As the size of patterns is getting smaller, influence between adjacent patterns during the photolithography process causes an optical proximity effect. Accordingly, an optical proximity correction (OPC) is executed to correct a layout designed by a designer and to suppress pattern distortion caused by the optical proximity effect.
A process of optical proximity correction starts with designing a layout of target patterns to be projected on a wafer and fabricating a test mask having test patterns. Patterns are formed on the wafer by performing a wafer process using the test mask and the line widths of the patterns formed on the wafer are measured. A model calibration for the optical proximity correction is executed using the data on the measured line widths. An optimal recipe necessary for the optical proximity correction is written using the calibrated model. The optical proximity correction is executed using the calibrated model and the recipe, and it is verified whether the optical proximity correction was properly executed. It is, then, decided whether an error detected during the verification process is within a range of an error tolerance.
If the error detected during the verification process is outside the range of the error tolerance, the optical proximity correction is re-executed in all areas of the mask by re-executing the model calibration and correcting the recipe. At this time, after the optical proximity correction is completed, the error may be outside the range of the error tolerance, in only a specific pattern or area. Nevertheless, according to the conventional optical proximity correction process, the optical proximity correction is re-executed again for the entire wafer chip using a new model or a new recipe in order to correct a specific pattern or area. As patterns become finer and more complex, executing the optical proximity correction becomes increasingly time consuming. Accordingly, an improved optical proximity correction is required to reduce the time for fabricating a mask.